Electronic devices typically make use of both analog and digital signals. An analog signal is a continuous signal which may assume any value. A digital signal is one which assumes one of a discrete set of values. A signal may be in the form of an electrical current or a voltage. Electronic circuitry often includes devices for transferring analog signals into digital signals and vice versa. For example, an Analog-to-Digital Converter (ADC) transfers analog signals into digital signals while a Digital-to-Analog Converter (DAC) transfers digital signals into analog signals.
One type of ADC is a pipelined ADC. A pipelined ADC uses a series of stages, each stage determining a sub-set of bits from the final digitized value. For example, a pipelined ADC may convert an analog signal into a sixteen-bit digital signal. The pipelined ADC may include four stages, each stage extracting four bits to add to the total digital word. The earlier stages extract the most significant bits while the later stages convert the least significant bits.
Each stage includes a sub-ADC to convert the appropriate number of bits from that stage. A sub-DAC is then used to create an analog version of the newly converted digital signal. This analog version of the newly converted digital signal is then subtracted from the original signal. The remaining signal, which is referred to as the residue signal, is then sent to subsequent stages for further processing.
Throughout the drawings, identical reference numbers designate similar, but not necessarily identical, elements.